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Abstract:

An object of the present invention is to provide a tube which can be
easily torn and has a large heat-shrinkability at a low temperature. The
tube of the present invention is a heat-shrinkable tube having
tearability, including a mixture of a fluorine resin and a different kind
of resin from the fluorine resin, in which an amount of change in loss
energy, ΔE loss, with change in temperature from 175° C. to
185° C. is a positive value.

Claims:

1. A heat-shrinkable tube having tearability, comprising a mixture of a
fluorine resin and a different kind of resin from the fluorine resin,
wherein when a sine vibration stress with a cycle of 30 sec and an
amplitude of 10 g is applied and a temperature is raised at rate of
5.degree. C./min, an amount of change in loss energy, ΔE loss, with
change in temperature from 175.degree. C. to 185.degree. C. is a positive
value

2. The heat-shrinkable tube having tearability of claim 1, wherein the
ΔE loss is 0.05 μJ or more.

3. The heat-shrinkable tube having tearability of claim 1, wherein a
storage elastic modulus at 50.degree. C. is 100 MPa or less.

4.-8. (canceled)

Description:

TECHNICAL FIELD

[0001] The present invention relates to a heat-shrinkable tube having
tearability which is made of a fluorine resin, and more particularly to a
tearable tube having heat shrinkability in which a material of the tube
is a thermoplastic fluorine resin.

BACKGROUND ART

[0002] A tearable tube has been used as a protective member for various
articles until the articles are used. Among them, a tearable tube made of
a fluorine resin has properties such as heat resistance, chemical
resistance, water and oil repellency, non-adhesion, self-lubricity or the
like which cannot be obtained with a tearable tube made of
hydrocarbon-based synthetic resin.

[0003] Therefore, by using these properties, the tube has been used as a
protective tube for precision equipment, electronic components or the
like, or as a tube for introducing medical devices, which is used to
introduce a catheter, a guide wire or the like into a body. The tube for
introducing medical devices is unnecessary after a catheter or the like
is introduced into the body, and also there is a management problem for
maintaining the hygienic state. Thus, after the catheter is introduced
into the body, the tube has to be withdrawn while being torn.

[0004] A tearable tube is required to securely protect the device mounted
inside thereof, to be easily tearable without using a special device, and
to maintain the properties possessed by the fluorine resin. The
conventional tube in which a cut was made on its surface along with the
longitudinal direction was not easily torn. Thus, in Japanese Patent
Application Laid-Open No. 2008-20037, in order to easily tear without a
need for an excessively cut portion, there has been proposed an extruded
tube made of a fluorine resin which is obtained by extrusion molding a
mixture of a tetrafluoroethylene resin and a fluorine resin having a low
molecular weight. In order to coat the surface of a device such as a
catheter with a fluorine resin, the heat-shrinkable tube made of a
fluorine resin is needed to be heat-shrank by heating the tube after
coating its surface. However, when the shrinkage of the heat-shrinkable
tube is small, there is a problem that the close contact between the
heat-shrinkable tube and the device is insufficient and also workability
is deteriorated.

DISCLOSURE OF INVENTION

[0005] An object of the present invention is to provide a tearable tube
made of a fluorine resin, which can be easily torn, has a large
heat-shrinkability, can be ensured to be close contacted and coated by
heat shrinking when the tube is mounted in a device, and also can be
simply torn at time when the device is used.

[0006] The object of the present invention can be achieved by a
heat-shrinkable tube (1) having tearability, which includes a mixture of
a fluorine resin and a different kind of resin from the fluorine resin,
in which when a sine vibration stress with a cycle of 30 sec and an
amplitude of 10 g is applied and a temperature is raised at rate of
5° C./min, an amount of change in loss energy, LE loss, with
change in temperature from 175° C. to 185° C. is a positive
value.

[0007] In the tube (1), better tearability and heat-shrinkability can be
obtained by a tube (2) having a ΔE loss of 0.05 μJ or more.

[0008] In the tube (1), better tearability and heat-shrinkability can be
obtained by a tube (3) having a storage elastic modulus at 50° C.
of 100 MPa or less.

[0009] The object of the invention can be achieved by a heat-shrinkable
tube (4) having tearability, which includes a mixture of different kinds
of fluorine resins, in which a main fluorine resin is a polymer made of
at least three kinds of monomers and contains at least a
tetrafluoroethylene and a hexafluoropropylene as constituent monomer
units.

[0010] In the tube (4), better tearability and heat-shrinkability can be
obtained by a tube (5) in which the main fluorine resin contains at least
a tetrafluoroethylene, a hexafluoropropylene and a perfluoroalkylvinyl
ether as constituent monomer units.

[0011] In the tube (4), better tearability and heat-shrinkability can be
obtained by a tube (6) in which the main fluorine resin contains at least
a tetrafluoroethylene, a hexafluoropropylene and a vinylidene fluoride as
constituent monomer units and has a glass transition temperature is
40° C. or higher.

[0012] In the tube (4), better tearability and heat-shrinkability can be
obtained by a tube (7) in which a fluorine resin other than the main
fluorine resin contains at least a tetrafluoroethylene-ethylene copolymer
or a polyvinylidene fluoride.

[0013] In the tube (4), better tearability and heat-shrinkability can be
obtained by a tube (8) in which a mixing ratio of the main fluorine resin
and a resin other than the main fluorine resin is from 98:2 to 70:30 by
mass ratio.

[0014] The object of the present invention can be achieved by a
heat-shrinkable tube having tearability which contains a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether
copolymer as a main component and further contains a
tetrafluoroethylene-ethylene copolymer. In the tube, the mixing ratio of
the tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether
copolymer and the tetrafluoroethylene-ethylene copolymer is from 98:2 to
70:30 by mass ratio.

[0015] The tearable tube made of the fluorine resin of the present
invention has good heat-shrinkability at a low temperature of about
200° C. along with tearability, so that the tube may be mounted
tightly on a mounting member when the tube is provided in a device, and
may be excellent in handlability. Further, the tearable tube made of the
fluorine resin of the present invention can be manufactured by
melt-extruding a raw material blended with different kinds of
thermoplastic fluorine resins, so that the tearable tube made of the
fluorine resin which is easily produced and has a stable tear
characteristics may be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a diagram related to DMA measurements according to the
present invention for illustrating a sinusoidal wave stress.

[0017] FIG. 2 is a diagram representing a relationship between stress and
strain when the sinusoidal wave stress is applied to a sample.

[0018] FIG. 3 is a graph showing a viscoelasticity of the tube of Example
1.

[0019] FIG. 4 is a graph showing a viscoelasticity of the tube of
Comparative Example 1.

[0020] FIG. 5 is a graph showing a viscoelasticity of the tube of Example
3.

MEANS FOR CARRYING OUT THE INVENTION

[0021] A heat-shrinkable tube having tearability is disclosed in Japanese
Patent Application Laid-Open No. 2008-20037. However, the thermal
shrinkage (a change rate of the inner diameter) of the disclosed tube
therein is 30% at most, and this cannot be said to be sufficient.

[0022] As for the tube of the present invention, a thermal shrinkage at a
low temperature of about 200° C. may be 40% or more, and ΔE
loss>0 is important for that. The aggregation structure of molecular
chain which could not be collapsed near the glass transition temperature
(at a low temperature side) will be released gradually at a high
temperature side of 150° C. or higher, so that strain of the
object due to an external force becomes larger. "ΔE loss>0"
means that the increase of such strain is led to an increase in loss
energy at the high temperature side. Further, from another perspective,
it means that in the tube of the present invention, the molecules may
move freely to some extent while maintaining a certain degree of
entanglement between the molecules even at around 200° C. It is
considered that when the tube is heated to around 200° C., it is
easy to return to the state of the molding due to such properties, and
thus, high shrinkage ratio may be obtained. Here, the ΔE loss means
an amount of change in loss energy with change in temperature from
175° C. to 185° C. when a sine vibration stress is applied
and a temperature is raised at rate of 5° C./min. The measurement
sample is not the tube as it is, but is obtained by hot melt pressing the
tube. Since the measurement sample is subjected to thermal hysteresis,
measurement is performed to obtain a change in loss energy at around
180° C. at a lower temperature side instead of the change in loss
energy at around 200° C. where the heat shrink is performed. The
conventional tubes take ΔE loss of a negative value. In such
conventional products, since the entanglement of molecular chains is
almost missing at a high temperature side of 150° C. or higher, an
action of return to the state at the time of molding hardly occurs, and
as a result thermal shrinkage is low. When ΔE loss is 0.05 μJ or
more, it is preferred in that higher thermal shrinkage may be obtained.
When ΔE loss is 0.2 μJ or more, it can be said to be a more
preferred embodiment. ΔE loss is highly dependent on the
characteristics of a "main fluorine resin" to be described later.

[0023] The heat-shrinkable tube having tearability of the present
invention would be expanded after molding the tube. If the elastic
modulus is too high at that time, the tube may return to its original
size momentarily even though the tube is expanded. As a result, a high
expansion ratio is hardly obtained, and thus, a high thermal shrinkage is
hardly obtained as well. The elastic modulus at 50° C. is
preferably 100 MPa or less.

[0024] As a material of the main fluorine resin in which the thermal
shrinkage is large at a low temperature of 200° C., a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer is exemplified. The main fluorine resin as mentioned herein
means a resin having the highest mixing ratio among a plurality of
different kinds of fluorine resins. The above mentioned copolymer is a
terpolymer obtained by adding a perfluoroalkyl vinyl ether monomer in a
monomer constituting a tetrafluoroethylene-hexafluoropropylene copolymer
(FEP). The perfluoroalkyl vinyl ether moiety is closely intertwined with
other molecules to form an aggregation structure of molecular chain. By
the aggregation structure of molecular chain, when the structure is
heated to 200° C. in an expanded state at 100° C. after
molding, the force to return to the size at the time of molding is
applied. Here, from the viewpoint whether an appropriate aggregation
structure of molecular chains is generated, the glass transition
temperature (Tg) of the
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer is preferably 68° C. or higher. On the other hand, as
for the material having similar composition, the one obtained by blending
a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer with a binary
copolymer of a tetrafluoroethylene and a hexafluoropropylene may be
considered. However, the entanglement at a molecular level does not occur
just only by blending the copolymers, and thus, the effect of preventing
rupture at the time of high expansion cannot be expected.

[0025] The other materials of the main fluorine resin include a ternary
copolymer (THV) of a tetrafluoroethylene, a hexafluoropropylene and a
vinylidene fluoride (VDF). The THV is a terpolymer obtained by adding
further VDF to monomers constituting the FEP, the VDF portion thereof is
greatly polarized into positive and negative, and forming of the
aggregation structure of molecular chain starts from this portion. By the
aggregation structure of molecular chain, when the structure is heated to
200° C. from an expanded state at 100° C. after molding,
the force to return to the size at the time of molding is applied.
However, in the case of the THV, the glass transition temperature (Tg)
needs to be 40° C. or higher. It is more preferable that the Tg is
45° C. or higher. If the Tg is 40° C. or lower, the
aforementioned proper aggregation of molecular chain structure is not
made and thus the sufficient thermal shrinkage cannot be obtained. For
example, as seen in that THV221 manufactured by Dyneon of 3M Group has Tg
of 5° C., and THV610 manufactured by Dyneon of 3M Group has Tg of
34° C., Tg of conventional THV has become lower. In the case of
the THV, if the proportion of the tetrafluoroethylene is increased, Tg
tends to increase.

[0026] A quaternary copolymer (quaternary THV) of
tetrafluoroethylene-hexafluoropropylene-vinylidene
fluoride-perfluoroalkyl vinyl ether also tends to be similar to THV.

[0027] As described above, in the case of ternary or higher polymers, the
aggregation structure of molecular chain may be easily made, and thus,
the object of the present invention may be achieved.

[0028] It is not clear why the heat-shrinkable tube made of fluorine resin
having a high shrinkage and excellent characteristics is obtained by
blending the ternary (quaternary) copolymer containing fluorine as in the
present invention. However, the perfluorovinyl ether component (PVE) in a
ternary copolymer, for example, in a
tetrafluoroethylene-hexafluoropropylene copolymer increases the
entanglement of molecules. Thus, it is believed that the heat-shrinkable
tube is less likely to be ruptured even when the tube highly expanded and
this is one of the causes.

[0029] Further, as reviewed with respect to the reason why the tube having
tearability which has excellent characteristics can be obtained by the
present invention, it is considered that the reason is the difference
between the lengths of the C--F bonds or C--H bonds in the molecule of
each of different kinds of fluorine resins, or due to the compatibility
between the fluorine resins having a difference in the cohesive energy.
Therefore, the fluorine resin combined with the main fluorine resin may
be, but not limited thereto, a resin which 1) has a close melting point,
2) is not compatible, and 3) has a difference between the length of the
C--F bonds or the C--H bonds in the molecule or a difference in cohesive
energy in the relationship with the main fluorine resin. For example, the
combination of the fluorine resin combined with the main fluorine resin
includes a combination of a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer and a tetrafluoroethylene-ethylene copolymer, a combination of
the THV and a polyvinylidene fluoride (PVDF), but not limited thereto. As
for the resin combined with the main fluorine resin, any resin other than
the fluorine resin may be available, as long as the resin 1) has a close
melting point and 2) is incompatible. However, a fluorine resin, which
has a similar basic structure to that of the main fluorine resin and may
be different in terms of the cohesive energy, is more preferable.

[0030] An aspect of the present invention includes a heat-shrinkable tube
having tearability which contains a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer and a tetrafluoroethylene-ethylene copolymer, and another
aspect includes a heat-shrinkable tube having tearability which contains
THV and PVDF.

[0031] Further, by setting the mixing ratio of the main fluorine resin
(e.g., a tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl
ether copolymer) and the fluorine resin other than the main fluorine
resin (e.g., a tetrafluoroethylene-ethylene copolymer) to a range from
98:2 to 70:30 by mass ratio, the heat-shrinkable tube having tearability
made of the fluorine resin which has significantly excellent
heat-shrinkability and tearability may be obtained. Furthermore, the
mixing ratio of the main fluorine resin (e.g., a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer) and the fluorine resin other than the main fluorine resin
(e.g., a tetrafluoroethylene-ethylene copolymer) is more preferably from
98:2 to 80:20, and still more preferably from 95:5 to 80:20.

[0032] As for the heat-shrinkable tube having tearability made of the
fluorine resin of the present invention, it is possible to, after the raw
materials are blended, perform the tube forming by a sizing plate method
using a single-screw melt extruder having a cylinder diameter of 20 mm at
a screw rotation speed of 10 rpm.

[0033] The temperature conditions may be set to a die temperature of
360° C. to 400° C.

[0034] Further, it is possible to increase the stability during molding by
changing the temperature in consideration of the molding conditions
depending on the mixing ratio of the resins.

[0035] Then, it is possible to impart the heat-shrinkability by filling
pressurized nitrogen inside the shaped tube made of the fluorine resin so
as to expand the tube. The pressure of the gas supplied inside the tube
made of the fluorine resin when the tube is expanded may be applied by
supplying the pressure in the range in which each of the tube made of a
fluorine resin is not destroyed.

[0036] Hereinafter, the present invention will be described as shown in
Examples and Comparative Examples.

EXAMPLES

[0037] (1) Loss Energy, Elastic Modulus, and tan δ

[0038] The viscoelastic data was obtained by a DMA (dynamic
viscoelasticity) measurement using a thermal mechanical analyzer,
TMA4000, manufactured by Bruker AXS, Inc.

[0039] <Measurement Sample>

[0040] Fabrication method: a measurement sample was obtained by melt
pressing a test tube with a thermal press manufactured by Toho Machinery
Co., Ltd. which was set to a temperature of 310° C. (however,
260° C. in Example 3) and a pressure of 200 to 400 N/cm2, and
then by immediately water-cooling the tube with a water-cooled press.

[0041] Size (length×width×thickness): 20 mm×5
mm×200 to 400 μm

[0042] <Fixation of Sample>

[0043] Distance between the chucks: 15 mm.

[0044] <Temperature Program>

[0045] Rate of temperature increase: 5° C./min

[0046] <Loading Program>

[0047] Loading mode: loading cycle of a sine wave (periodic stress)

[0048] Offset value: -3 g

[0049] Amplitude: 10 g (-3 to -13 g)

[0050] Cycle: 30 sec

[0051] * See FIG. 1.

[0052] <Analysis Method>

[0053] If the data of the stress and the strain when a sine wave stress
was applied to the sample is represented in a stress-strain coordinates
for one cycle, an ellipse is drawn as illustrated in FIG. 2.

[0054] Here, the slope of the ellipse represents an elastic modulus, and
the area of the ellipse represents a loss energy. The tan .5 is obtained
by a phase difference between the stress data and the strain data.

[0055] In the accessory analysis software, the calculation of the
viscoelastic data for each cycle is performed by dividing the data per
one cycle automatically from the measured data.

[0056] (2) Glass Transition Temperature

[0057] From the tan δ chart by the above-mentioned DMA measurement,
the temperature corresponding to the peak was determined as the glass
transition temperature.

Example 1

[0058] (Preparation of Sample)

[0059] Mixtures of a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer (FEP-130J produced by Du Pont-Mitsui Fluorochemicals Co., Ltd.,
Tg of 72° C.) and a tetrafluoroethylene-ethylene copolymer (ETFE:
C-55AP produced by Asahi Glass Co., Ltd.) were prepared by varying their
mixing ratio. Each mixture was shaped into pellets by using a biaxial
extruder having a cylinder diameter of 20 mm, at a screw rotation speed
of 45 rpm and at the die temperature of 320° C. The pellets were
used and tube forming was performed by a sizing plate method using a
single screw extruder having a cylinder diameter of 20 mm at a screw
rotation speed of 10 rpm and at the die temperature of 390° C. As
a result, samples having an inner diameter of 0.5 mm, an outer diameter
of 0.9 mm, and a thickness of 0.2 mm were produced.

[0060] (Test of Tear Strength)

[0061] After checking whether the samples were torn by hands without using
instruments, as for samples that could not be torn by hand only, the
incision was made with a razor and then whether the tearing from the
incision portion is possible was tested. As for the sample in which the
tearing was possible, an incision of 40 mm was formed at one end of the
sample having a length of 100 mm, and the sample was torn at a rate of
200 mm/min by a tensile tester. The maximum force at that time was
measured as tear strength.

[0062] Further, the length which could be torn without breaking when the
sample was torn was measured as the tear straightness. Furthermore, the
measurement was performed three times on the samples of the same
composition to obtain a weighted average value. The results are shown in
Table 1.

[0064] The test tubes were prepared by changing the mixing ratio of raw
materials, and mounted on the expansion test apparatus, and the
pressurized nitrogen was injected inside the tubes to measure whether the
tubes are expandable without breakdown. The results are shown in the
following table.

[0065] As for the mixture of a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer (FEP-130J produced by Du Pont-Mitsui Fluorochemicals Co., Ltd.)
and a tetrafluoroethylene-ethylene copolymer (ETFE: C-55AP produced by
Asahi Glass Co., Ltd.) used in the test, if the
tetrafluoroethylene-ethylene copolymer was not less than 5% by mass of
the total, it was confirmed that the tearability and the
heat-shrinkability could be obtained.

[0066] Then, five samples in which the tetrafluoroethylene-ethylene
copolymer (ETFE) was contained by 5% by mass, 7% by mass, 10% by mass,
20% by mass, and 30% by mass of the total, respectively, were prepared,
the pressurized nitrogen was applied to each sample, the samples were
expanded as large as possible so as not to be destroyed, and then their
sizes were measured. Subsequently, each sample was heat-shrunk by heating
the sample under the conditions of 200° C. and 20 min, and the
size after its heat shrink was measured in the same manner. As for
Samples 2-1 to 2-5 in which the concentration of the ETFE is 5% by mass,
the results are shown in Table 2. Further, as for Samples 3-1 to 3-5 in
which the concentration of the ETFE is 7% by mass, the results are shown
in Table 3. In addition, as for Samples 4-1 to 4-5 in which the
concentration of the ETFE is 10% by mass, the results are shown in Table
4. Further, as for Samples 5-1 to 5-5 in which the concentration of the
ETFE is 20% by mass, the results are shown in Table 5. Moreover, as for
Samples 6-1 to 6-5 in which the concentration of the ETFE is 30% by mass,
the results are shown in Table 6.

[0067] Meanwhile, as for the samples in which the concentration of the
ETFE is 40% by mass and 30% by mass, the resin is easily fiberized by
pellet forming and thus the pelletization is difficult to be performed.
As far in terms of productivity, the upper limit is considered to be up
to about 20% by mass for stable manufacturing range.

[0069] Mixtures of a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer (FEP-NP120 produced by Daikin Industries, Ltd., Tg of
74° C.) and a tetrafluoroethylene-ethylene copolymer (ETFE: C-55AP
produced by Asahi Glass Co., Ltd.) were prepared by varying their mixing
ratio. Each mixture was used and shaped into pellets by using a biaxial
extruder having a cylinder diameter of 20 mm, at a screw rotation speed
of 45 rpm and at the die temperature of 320° C.

[0070] Next, the obtained pellets were used and tube forming was performed
by a sizing plate method using a single screw extruder having a cylinder
diameter of 20 mm at a screw rotation speed of 10 rpm and at the die
temperature of 390° C. As a result, Samples 7-1 to 7-4 having an
inner diameter of 0.5 mm, an outer diameter of 0.9 mm, and a thickness of
0.2 mm were produced.

[0071] (Test of Tear Strength)

[0072] After checking whether the tearing from the incision portion is
possible or not by putting the incision with a razor, as for the sample
in which the tearing was possible, an incision of 40 mm was formed at one
end of the sample having a length of 100 mm, and the sample was torn at a
rate of 200 mm/min by a tensile tester. The maximum force at that time
was measured as tear strength. Further, the measurement was performed
three times on the samples of the same composition to obtain a weighted
average value. The results are shown in Table 7. Furthermore, the length
of samples which could be torn without breaking was shown in Table 7 as
the tear straightness when the samples having incisions put with a razor
were torn.

[0074] The test tubes were prepared by changing the mixing ratio of raw
materials, and mounted on the expansion test apparatus, and the
pressurized nitrogen was injected inside the tubes to measure whether the
tubes are expandable without breakdown. The results are shown in the
following table.

[0075] As for the prepared mixture of a tetrafluoroethylene-ethylene
copolymer (ETFE: C-55AP produced by Asahi Glass Co., Ltd.) and a
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
copolymer (FEP-NP120 produced by Daikin Industries, Ltd.), if the
tetrafluoroethylene-ethylene copolymer was not less than 2% by mass of
the total, it was confirmed that the tearability and the
heat-shrinkability could be obtained.

[0076] Then, five samples in which the tetrafluoroethylene-ethylene
copolymer (ETFE) was 2% by mass, 5% by mass, 7% by mass, and 10% by mass
of the total, respectively, were prepared, the pressurized nitrogen was
applied to each sample, the samples were expanded as large as possible so
as not to be destroyed, and then their sizes were measured. Subsequently,
each sample was heat-shrunk by heating the sample under the conditions of
200° C. and 20 min, and the size after its heat shrink was also
measured in the same manner.

[0077] As for Samples 8-1 to 8-5 in which the concentration of the ETFE is
2% by mass, the results are shown in Table 8. As for Samples 9-1 to 9-5
in which the concentration of the ETFE is 5% by mass, the results are
shown in Table 9. As for Samples 10-1 to 10-5 in which the concentration
of the ETFE is 7% by mass, the results are shown in Table 10. Further, as
for Samples 11-1 to 11-5 in which the concentration of the ETFE is 10% by
mass, the results are shown in Table 11.

[0078] (Preparation of Sample) Mixtures of a
tetrafluoroethylene-hexafluoropropylene copolymer (FEP-100J produced by
Du Pont-Mitsui Fluorochemicals Co., Ltd.) and a
tetrafluoroethylene-ethylene copolymer (ETFE: C-88AX produced by Asahi
Glass Co., Ltd.) were prepared by varying their mixing ratio. Each
mixture was used and tube forming was performed by a sizing plate method
using a single screw extruder having a cylinder diameter of 20 mm at a
screw rotation speed of 10 rpm and at the die temperature of 390°
C. As a result, samples having an inner diameter of 1.0 mm, an outer
diameter of 1.4 mm, and a thickness of 0.2 mm were produced.

[0079] (Test of Tear Strength)

[0080] After checking whether the tearing is possible or not only by hands
without using instruments or whether the tearing from the incision
portion is possible or not by putting an incision with a razor, as for
the things in which the tearing was possible, an incision of 40 mm was
formed at one end of the sample having a length of 100 mm, and the sample
was torn at a rate of 200 mm/min by a tensile tester. The maximum force
at that time was measured as tear strength. Further, the measurement was
performed three times on the samples of the same composition to obtain a
weighted average value. The results are shown in Table 12.

[0082] The pressurized nitrogen was injected inside the shaped tubes by
expansion means to determine whether the tubes are expandable without
breakdown. As for the mixture of a tetrafluoroethylene-ethylene copolymer
(ETFE: C-88AX produced by Asahi Glass Co., Ltd.) and a
tetrafluoroethylene-hexafluoropropylene copolymer (FEP-100J produced by
Du Pont-Mitsui Fluorochemicals Co., Ltd.) used in the test, if the
tetrafluoroethylene-ethylene copolymer took from 3% by mass to 10% by
mass of the total, it was confirmed that the tearability and the
heat-shrinkability could be obtained.

[0083] Then, five samples in which a tetrafluoroethylene-ethylene
copolymer (ETFE) was 10% by mass of the total were prepared, the
pressurized nitrogen was applied to each sample, the samples were
expanded as large as possible so as not to be destroyed, and then their
sizes were measured. Subsequently, each sample was heat-shrunk by heating
the sample under the conditions of 200° C. and 20 min, and the
size after its heat shrink was also measured in the same manner. As for
Samples 13-1 to 13-5 in which the concentration of the ETFE is 10% by
mass, the results are shown in Table 13.

[0085] Mixtures of a terpolymer (THV: Tg of 46° C.) of about 10
mol% of vinylidene fluoride, about 70 mol % of tetrafluoroethylene and
about 20 mol % of hexafluoropropylene, and a polyvinylidene fluoride
(PVDF: KYNAR 740 produced by ARKEMA (Arkema)) was prepared by varying
their mixing ratio. Each mixture was used and shaped into pellets by
using a biaxial extruder having a cylinder diameter of 20 mm, at a screw
rotation speed of 45 rpm and at the die temperature of 280° C.

[0086] Next, the obtained pellets were used and tube forming was performed
by a sizing plate method using a single screw extruder having a cylinder
diameter of 20 mm at a screw rotation speed of 10 rpm and at the die
temperature of 340° C. As a result, samples of 14-1 to 14-3 having
an inner diameter of 0.5 mm, an outer diameter of 0.9 mm, and a thickness
of 0.2 mm were produced.

[0087] (Test of Tear Strength)

[0088] After checking whether the tearing from the incision portion is
possible or not by putting the incision with a razor, as for the sample
in which the tearing was possible, the incision of 40 mm was formed at
one end of the sample having a length of 100 mm, and the sample was torn
at a rate of 200 mm/min by a tensile tester. The maximum force at that
time was measured as tear strength. Further, the measurement was
performed three times on the samples of the same composition to obtain a
weighted average value. The results are shown in Table 14.

[0090] The test tubes were prepared by changing the mixing ratio of raw
materials, and mounted on the expansion test apparatus, and the
pressurized nitrogen was injected inside the tubes to determine whether
the tubes are expandable without breakdown. The results are shown in the
following table. As for the mixture of a polyvinylidene fluoride (PVDF:
KYNAR 740 produced by ARKEMA (Arkema)) and the THV produced in this
example, if the polyvinylidene fluoride was not less than 2% by mass of
the total, it was confirmed that the tearability and the
heat-shrinkability could be obtained.

[0091] Then, samples in which polyvinylidene fluoride (PVDF) was 2% by
mass, 20% by mass, and 30% by mass of the total, respectively, was
prepared, the pressurized nitrogen was applied to each sample, the
samples were expanded as large as possible so as not to be destroyed, and
then their sizes were measured. Subsequently, each sample was heat-shrunk
by heating the sample under the conditions of 200° C. and 20 min,
and the size after its heat shrink was also measured in the same manner.

[0092] As for Sample 15-1 in which the concentration of the PVDF is 2% by
mass, the results are shown in Table 15. As for Sample 16-1 in which the
concentration of the PVDF is 20% by mass, the results are shown in Table
16. As for Sample of 17-1 in which the concentration of the PVDF is 30%
by mass, the results are shown in Table 17.

[0094] Since the tearable tube made of the fluorine resin of the present
invention has an excellent tearability and heat-shrinkability, the tube
may be mounted tightly on a mounting member when the tube is provided in
a device, and may be excellent in handlability. Further, since the
tearable tube made of the fluorine resin of the present invention may be
manufactured by melt-extruding a raw material blended with different
kinds of thermoplastic fluorine resins, it is possible to provide a
tearable tube made of the fluorine resin which is able to be easily
produced and has a stable tear characteristics.